System and Method for Wireless Link Configuration

ABSTRACT

A method for operating a relay node during a handoff from a first controller to a second controller includes receiving a first instruction from the first controller to discontinue using a first set of wireless backhaul link resources allocated to the relay node by the first controller and to temporarily use a second set of wireless backhaul link resources dedicated by the second controller. The method also includes receiving a second instruction from the second controller to discontinue using the second set of wireless backhaul link resources and to begin using a third set of wireless backhaul link resources allocated to the relay node by the second controller.

TECHNICAL FIELD

The present invention relates generally to digital communications, andmore particularly to a system and method for wireless linkconfiguration.

BACKGROUND

Within the context of the Third Generation Partnership Project (3GPP)Long Term Evolution (LTE) Release 10, Relay Nodes (RNs) arestandardized. Generally, RNs are network nodes that communicate with anenhanced NodeB (eNB), which may also be commonly referred to as acommunications controller, a base station, a NodeB, a controller, andthe like, through a wireless link referred to as a Un link or a wirelessbackhaul, which may be in-band or out-of-band. To a User Equipment (UE),which may also be commonly referred to as a mobile station, terminal,subscriber, user, and the like, the RNs may appear as eNBs. The RNs areconsidered to be tools to improve, e.g., the coverage area of high datarate communications, group mobility, temporary network deployment, thecell-edge throughput, and/or to provide coverage in new areas.

Typically, there may be two types of RNs: fixed RNs and mobile RNs(mRNs). As their names imply, a fixed RN may be deployed in a fixedlocation and serve UEs operating within its operating area, while a mRNmay be deployed in a mobile location and serve UEs operating with itsmoving operating area. The UEs operating within the moving operatingarea of the mRN may be moving along with the mRN or moved into themoving operating area of the mRN.

SUMMARY OF THE INVENTION

Technical advantages are generally achieved by embodiments of thepresent invention which provide a system and method for wireless linkconfiguration.

In accordance with an example embodiment of the present invention, amethod for operating a relay node during a handoff from a firstcontroller to a second controller is provided. The method includesreceiving a first instruction from the first controller to discontinueusing a first set of wireless backhaul link resources allocated to therelay node by the first controller and to temporarily use a second setof wireless backhaul link resources dedicated by the second controller.The method also includes receiving a second instruction from the secondcontroller to discontinue using the second set of wireless backhaul linkresources and to begin using a third set of wireless backhaul linkresources allocated to the relay node by the second controller.

In accordance with another example embodiment of the present invention,a method for operating a method for operating a target controller duringa handoff of a relay node is provided. The method includes receiving thehandoff of the relay node from a source controller, and instructing therelay node to temporarily use a first set of wireless backhaul linkresources dedicated by the target controller upon completion of thehandoff. The method also includes transmitting an allocation of a secondset of wireless backhaul link resources to the relay node.

In accordance with another example embodiment of the present invention,a relay node is provided. The relay node includes a receiver, and aprocessor operatively coupled to the receiver. The receiver receives afirst instruction from a first controller to discontinue using a firstset of wireless backhaul link resources allocated to the relay node bythe first controller and to temporarily use a second set of wirelessbackhaul link resources dedicated by a second controller, and receives asecond instruction from the second controller to discontinue the use ofthe second set of wireless backhaul link resources and to begin the useof a third set of wireless backhaul link resources allocated to therelay node by the second controller. The processor temporarily uses thesecond set of wireless backhaul link resources dedicated by the secondcontroller, and uses the third set of wireless backhaul link resourcesallocated to the relay node by the second controller.

In accordance with another example embodiment of the present invention,a communications controller is provided. The communications controllerincludes a processor, and a transmitter operatively coupled to theprocessor. The processor receives a handoff of a relay node from asource controller, and instructs the relay node to temporarily use afirst set of wireless backhaul link resources dedicated by thecommunications controller upon completion of the handoff. Thetransmitter transmits an allocation of a second set of wireless backhaullink resources to the relay node.

In accordance with another example embodiment of the present invention,a method for operating a relay node during a handoff from a sourcecontroller to a target controller is provided. The method includesreceiving, from a source controller, backhaul link information includingan allocation of a target set of wireless backhaul link resources of thetarget controller dedicated for use of the relay node upon completion ofthe handoff. The method also includes receiving backhaul link data fromthe target controller over the target set of wireless backhaul linkresources.

In accordance with another example embodiment of the present invention,a method for operating a target controller during a handoff of a relaynode is provided. The method includes transmitting, to a sourcecontroller, backhaul link information including an allocation of atarget set of wireless backhaul link resources dedicated for use by therelay node upon completion of the handoff. The method also includestransmitting, to the relay node, backhaul link data over the target setof wireless backhaul link resources.

In accordance with another example embodiment of the present invention,a relay node is provided. The relay node includes a receiver, and aprocessor operatively coupled to the receiver. The receiver receives,from a source controller, backhaul link information including anallocation of a target set of wireless backhaul link resources of atarget controller dedicated for use of the relay node upon completion ofa handoff, and receives backhaul link data from the target controllerover the target set of wireless backhaul link resources. The processorprocesses the backhaul link data.

In accordance with another example embodiment of the present invention,a communications controller is provided. The communications controllerincludes a transmitter, and a processor operatively coupled to thetransmitter. The transmitter transmits, to a source controller, backhaullink information including an allocation of a target set of wirelessbackhaul link resources dedicated for use by a relay node uponcompletion of a handoff, and transmits, to the relay node, backhaul linkdata over the target set of wireless backhaul link resources. Theprocessor generates the backhaul link data.

One advantage of an embodiment is that mRN handovers between two eNBs (asource eNB and a target eNB) may occur rapidly without incurringsignificant delay that is typically required for configuring thebackhaul link for the mRN in the target eNB. The delay may dramaticallyimpact the performance of the mRN, especially in situations wherein themRN is rapidly moving between eNBs, such as when the mRN is deployed ona high speed train.

A further advantage of an embodiment is that the rapid configuration ofthe backhaul link helps to increase the handoff success rate, especiallyin situations wherein the mRN is rapidly moving between eNBs.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawing, in which:

FIG. 1 illustrates an example first communications system according toexample embodiments described herein;

FIG. 2 illustrates an example portion of a communications systemaccording to example embodiments described herein;

FIG. 3 illustrates an example sequence of frames according to exampleembodiments described herein;

FIG. 4 illustrates example first sequence of frames and a secondsequence of frames according to example embodiments described herein;

FIG. 5 a illustrates an example flow diagram of mRN operations accordingto example embodiments described herein;

FIG. 5 b illustrates an example flow diagram of eNB operations accordingto example embodiments described herein;

FIG. 6 illustrates example first sequence of frames and a secondsequence of frames according to example embodiments described herein;

FIG. 7 illustrates an example flow diagram of mRN operations accordingto example embodiments described herein;

FIG. 8 a illustrates an example flow diagram of eNB operations inproviding Un link subframe allocation to an mRN according to exampleembodiments described herein;

FIG. 8 b illustrates an example flow diagram of eNB operations accordingto example embodiments described herein;

FIG. 9 illustrates an example communications device according to exampleembodiments described herein; and

FIG. 10 illustrates an example communications controller according toexample embodiments described herein.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The operating of the current example embodiments and the structurethereof are discussed in detail below. It should be appreciated,however, that the present invention provides many applicable inventiveconcepts that can be embodied in a wide variety of specific contexts.The specific embodiments discussed are merely illustrative of specificstructures of the invention and ways to operate the invention, and donot limit the scope of the invention.

One embodiment of the invention relates to providing wireless backhaullink configuration information to a mRN during a handoff process. Forexample, at two eNBs (a source eNB and a target eNB) involved in thehandoff, both eNBs may share at least some subframes (which may bereferred to as wireless backhaul link resources) in their respectivewireless backhaul link configurations. Therefore, the mRN may be able toimmediate use at least a portion of the wireless backhaul link of thetarget eNB as soon as it finishes the handoff procedure instead ofhaving to wait for the target eNB to provide its wireless backhaul linkinformation. As another example, the target eNB may share its wirelessbackhaul link configuration with the source eNB, which in turn, providesthe wireless backhaul link configuration of the target eNB to the mRN.The mRN may then make use of the wireless backhaul link configuration ofthe target eNB as soon as it finishes the handoff procedure instead ofhaving to wait for the target eNB to provide its wireless backhaul linkinformation.

The present invention will be described with respect to exampleembodiments in a specific context, namely a Third Generation PartnershipProject (3GPP) Long Term Evolution (LTE) compliant communications systemthat supports Relay Nodes (RNs) and handoffs for mobile RNs (mRN). Theinvention may also be applied, however, to other standards compliant,such as WiMAX, IEEE 802.16m, and the like, communications systems, aswell as non-standards compliant communications systems that support RNsand handoffs for mRNs.

FIG. 1 illustrates a first communications system 100. Firstcommunications system 100 includes an enhanced NodeB (eNB) 105, a relaynode (RN) 110, a first User Equipment (UE) 115, and a second UE 120.While it is understood that communications systems may employ multipleeNBs capable of communicating with a number of UEs, only one eNB, twoUEs, and one RN are illustrated for simplicity.

A RN (fixed or mobile) is generally considered as a tool to improve,e.g., the coverage area of high data rate communications, groupmobility, temporary network deployment, the cell-edge throughput, and/orto provide coverage in new areas. The RN is wirelessly connected to awireless communications network via an eNB, such as eNB 105.

UE 115 and UE 120 may be communications devices that allow an operatorto connect to a service, such as voice service, data service, multimediaservice, and the like. As shown in FIG. 1, eNB 105 has allocated someresources to RN 110, which in turn, may allocate some resources(provided by eNB 105) to UE 120. eNB 105 may also directly communicatewith UEs. For example, eNB 105 directly allocates resources to UE 115.Communications between eNB 105 and RN 110 may be made over acommunications link (uplink and/or downlink directions) referred to as aUn link 120 or a wireless backhaul link, while communications between RN110 and UE 120 may be made over a communications link (uplink and/ordownlink directions) referred to as a Uu link 130 or an access link.Communications between eNB 105 and UE 115 may be made overcommunications link referred to as access link 135.

FIG. 2 illustrates a portion of a communications system 200.Communications system 200 includes a first eNB 205 (shown as eNB A) anda second eNB 210 (shown as eNB B). Communications system 200 alsoincludes a mRN 215 that may be a mRN. For example, mRN 215 may bedeployed on a rapidly moving bus, train, or the like. As mRN 215 movesaround, it may move out of a coverage area of one eNB and into acoverage area of another eNB. As shown in FIG. 2, mRN 215 may move outof the coverage area of first eNB 205 and into the coverage area ofsecond eNB 210.

In order to maintain a high level of service, the handoff between theeNBs may need to be fast, reliable, and as seamless as possible. Anissue that is associated with an mRN handoff is that the Un linksubframe allocation (i.e., the wireless backhaul link resources) may bedifferent between the two eNBs involved in the handoff. For discussionpurposes, the two eNBs involved in an mRN handoff may be referred to asa source eNB (the eNB currently serving the mRN as it moves out of theeNB's coverage area) and a target eNB (the eNB that will be serving themRN after the handoff completes). The target eNB may also be referred toas a new serving eNB once the handoff completes.

Therefore, once the mRN completes the handoff process, it is not able toutilize the Un link (and operate as a RN) until it determines the Unlink subframe allocation of its new serving eNB. Generally, obtainingthe Un link subframe allocation may be a relatively lengthy process. Thelengthy process may seriously impact the performance of the mRN for ahigh mobility mRN, such as one located on a high speed train, inparticular. As an example, on a high speed train moving at approximately300 kilometer per hour with cell diameters of 1 kilometer, the mRNswitches eNBs about once every 12 ms. Therefore, there is only a smallamount of time available for obtaining the Un link subframe allocationand provide adequate service. It is noted that the effect of having themRN not communicating has an impact on many UEs (e.g., all the UEscommunicating with the mRN). Therefore it is imperative to ensure ahandoff process for the nRM as fast and as reliable as possible.

The Un link subframe allocation is described herein for a frequencydivision duplexed (FDD) communications system. Extending the Un linksubframe allocation for a time division duplexed (TDD) communicationssystem is straightforward and is not described in detail herein.

According to Section 5.2 of the 3GPP LTE Release-10 technical standards,the Un link subframe allocation has a 40 ms periodicity and subframes 0,4, 5, and 9 may not be used as Un link subframes. Up to 8 basic subframesubsets may be allocated. Each basic subframe subset consists of 3subframes per 40 ms period. A bitmap may be used to indicate which basicsubframe subset(s) is (are) allocated. Table 1 displays the 8 basicsubframe subsets.

TABLE 1 Basic subsets for Un link subframe allocation. Patterns for UnDL subframes within 40 ms period link subframe Frame Frame Frame Frame8-bit bitmap allocation N N + 1 N + 2 N + 3 MSB 8th bit 0 8 6 2 7th bit1 1 7 3 6th bit 2 2 8 6 5th bit 3 3 1 7 4th bit 4 2 8 6 3rd bit 5 3 1 72nd bit 6 6 2 8 LSB 1st bit 7 7 3 1

FIG. 3 illustrates a sequence of frames 300. Sequence of frames 300consists of four consecutive frames (frame 4N, frame 4N+1, frame 4N+2,and frame 4N+3). Each frame in sequence of frames 300 consists of 10subframes numbered between 0 and 9. As shown in FIG. 3, some of thesubframes in sequence of frames 300 may be allocated for a Un link witha bitmap 0x00000101, which indicates that basic subsets 0 and 2 areallocated for the Un link. Basic subset 0 means that subframe 8 in frame4N, subframe 6 in frame 4N+1, and subframe 2 in frame 4N+3, areallocated for use as the Un link and basic subset 2 means that subframe2 in frame 4N, subframe 8 in frame 4N+1, and subframe 6 in frame 4N+2are allocated for use as the Un link.

According to an example embodiment, it may be possible to shorten aninterval of time between completion of an mRN handoff between the sourceeNB and the target eNB and when the mRN may be able to begin utilizingthe Un link by having the two eNBs have at least some common subframesin their respective Un link subframe allocations.

FIG. 4 illustrates a first sequence of frames 400 and a second sequenceof frames 405. First sequence of frames 400 represents four frameshighlighting a Un link subframe allocation for a source eNB and secondsequence of frames 405 represents four frames highlighting a Un linksubframe allocation for a target eNB. The Un link subframe allocationfor the source eNB may be referred to as S_(A), and the Un link subframeallocation for the target eNB may be referred to as S_(B). Some of thesubframes allocated for the Un link of the source eNB as shown in firstsequence of frames 400 are also allocated for the Un link of the targeteNB as shown in second sequence of frames 405, with the common subframesshown in FIG. 4 as subframes 410. The common subframes may also bereferred to as a minimum Un link subframe allocation. The minimum Unlink subframe allocation may be referred to as S_(φ), whereS_(A)∩S_(B)=S_(φ), S_(A)∩S_(φ)=S_(φ), and S_(B)∩S_(φ)=S_(φ). It is notedthat in an extreme case, a single Un link subframe allocation (i.e., theminimum Un link subframe allocation) may be used in all of the eNBs.

The common subframes may be shared by all eNBs in a communicationssystem or by a subset of all eNBs in the communications system and maybe provided to the mRN through signaling, such as higher layersignaling. Since the mRN knows the common subframes, as soon as thehandoff completes, the mRN may begin to operate as a RN by using thecommon subframes and the delay between the completion of the handoff andwhen the mRN may be able to begin utilizing the Un link may be small.

FIG. 5 a illustrates a flow diagram of mRN operations 500. mRNoperations 500 may be indicative of operations occurring in an mRN, suchas mRN 215, prior to a handoff, during the handoff, and after thehandoff between two eNBs.

Prior to the handoff, the mRN is being served by a source eNB and may bereceiving (and sending on corresponding uplink subframes) Un data onsubframes allocated for the Un link of the source eNB, i.e., S_(A)(block 505). Since the mRN knows S_(A), the mRN may receive the Un datawithout problems.

As the mRN moves about, it participates in the handoff with a target eNB(block 510). According to an example embodiment, the handoff istriggered by a message, e.g., a handoff initialization message, receivedfrom the source eNB. Since the source eNB and the target eNB share aminimum Un link subframe allocation, S_(o), as soon as the handoff iscomplete, the mRN may begin to receive (and sending on correspondinguplink subframes) Un data on S_(φ) from the target eNB (block 515).Therefore, there is very little delay between the completion of thehandoff and the beginning of receiving the Un data.

According to an example embodiment, rather than using the minimum Unlink subframe allocation, the mRN makes use of an agreed upon Un linksubframe allocation, that may be indicated to the mRN during or afterthe handoff. As an example, the target eNB may have previously agreed touse a Un link subframe allocation for new mRNs after a handoff until thetarget eNB has had a chance to signal its actual Un link subframeallocation. Each eNB may have its own agreed upon Un link subframeallocation, which may be stored in the eNBs and signaled to the mRNduring the handoff or immediately after the handoff. According to analternative embodiment, the mRN may store its own information regardingthe agreed upon Un link subframe allocations for the eNBs and utilizinginformation about the target eNB, the mRN determines the agreed upon Unlink subframe allocation that it will use until the target eNB providesinformation about its actual Un link subframe allocation.

While the mRN is receiving the Un data on S_(φ), the target eNB may besignaling the mRN its entire Un link subframe allocation, S_(B) (block520). Once the mRN receives the Un link subframe allocation S_(B) fromthe target eNB, the mRN may receive the Un data on the Un link subframeallocation S_(B) of the target eNB (block 525). According to an exampleembodiment, the signaling of the entire Un link subframe allocation isan implicit instruction from the target eNB to the mRN to discontinueusing the minimum Un link subframe allocation and begin to use theentire Un link subframe allocation. According to an alternative exampleembodiment, the target eNB sends an instruction to the mRN to instructthe mRN to discontinue using the minimum Un link subframe allocation andbegin to use the entire Un link subframe allocation.

FIG. 5 b illustrates a flow diagram of eNB operations 550. eNBoperations 550 may be indicative of operations occurring in a targeteNB, such as eNB B 210, during a handoff and after the handoff.

During the handoff, the target eNB and the mRN exchange signaling tocomplete the handoff (block 555). Once the handoff is complete, thetarget eNB may send Un data to the mRN over a minimum Un link subframeallocation, S_(φ), that is known by the mRN (block 560). According to analternative embodiment, the target eNB may send the Un data to the mRNover an agreed upon Un link subframe allocation. Since the mRN knows theminimum Un link subframe allocation S_(φ) for the target eNB, the targeteNB may not need to wait much time after the completion of the handoffbefore it sends the Un data.

The target eNB may also send its entire Un link subframe allocationS_(B) to the mRN (block 570). Once it has sent the Un link subframeallocation S_(B) to the mRN, the target eNB may use the Un link subframeallocation S_(B) to send Un data to the mRN (block 575).

According to an example embodiment, it may be possible to shorten aninterval of time between completion of an mRN handoff between two eNBsand when the mRN may be able to begin utilizing the Un link by havingneighboring eNBs share their Un link subframe allocations.

Generally, when there is a change in the Un link subframe allocation(e.g., when the mRN switches from the source eNB's Un link subframeallocation, S_(A), to the minimum Un link subframe allocation, S_(φ),and then to the target eNB's Un link subframe allocation, S_(B)) thenumber of Hybrid Automatic Repeat Requested (HARQ) processes may differ.Typically, if additional HARQ processes are needed, additional HARQprocesses may be added without much difficulty.

However, when there are more active HARQ processes than needed, theadditional unused HARQ processes may need to be addressed. Severaldifferent techniques may be used to address the additional unused HARQprocesses.

1. Stop the additional unused HARQ processes. As an example, if whileusing the source eNB's Un link subframe allocation the mRN uses 4 HARQprocesses and while using the minimum Un link subframe allocation themRN uses 2 HARQ processes, the two unused HARQ processes may be stopped.

2. Suspend the additional unused HARQ processes. Suspending theadditional unused HARQ processes may proceed as follows. Informationregarding the Un link subframe allocation from the source eNB may betransferred to the target eNB (e.g., using the backhaul). Then, whenswitching from the minimum Un link subframe allocation to the targeteNB's Un link subframe allocation, the suspended additional unused HARQprocesses may be resumed.

3. Operate conservatively or do not use HARQ at all when a handoff(which may be predictable based on operating conditions of the mRN or inhigh speed environments) is imminent. Once the handoff completes, themRN may resume normal operation and use HARQ.

4. Leave the additional unused HARQ processes for implementers of mRNs.

It is noted that in a handoff (or when using the minimum Un linksubframe allocation), even if the number of HARQ processes remainunchanged, the timing of the HARQ processes may be different. However,the differences in the timing of the HARQ processes may not be a problemsince the mRN may unequivocally determine the subframe mapping of theHARQ processes.

FIG. 6 illustrates a first sequence of frames 600 and a second sequenceof frames 605. First sequence of frames 600 represents four frameshighlighting a Un link subframe allocation for a source eNB and secondsequence of frames 605 represents four frames highlighting a Un linksubframe allocation for a target eNB. As shown in FIG. 6, the Un linksubframe allocation of the source eNB may not have any subframes incommon with the Un link subframe allocation of the target eNB. Althoughshown in FIG. 6 as not having any subframes in common, the Un linksubframe allocation of the source eNB may have some subframes in commonwith the Un link subframe allocation of the target eNB. However, thecommon subframes may not have been intentional.

FIG. 7 illustrates a flow diagram of mRN operations 700. mRN operations700 may be indicative of operations occurring in an mRN, such as mRN215, prior to a handoff, during the handoff, and after the handoffbetween two eNBs.

Prior to the handoff, the mRN is being served by a source eNB and may bereceiving (and sending on corresponding uplink subframes) Un data onsubframes allocated for the Un link of the source eNB, i.e., S_(A)(block 705). Since the mRN knows S_(A), the mRN may receive the Un datawithout problems.

As the mRN moves above, it may move into a periphery of a coverage areaof the source eNB. As a result, operating conditions of the mRN mayindicate to the source eNB that it is about to move out of the coveragearea of the source eNB and as a result, trigger a handoff from thesource eNB to a target eNB. The mRN may receive the Un link subframeallocation S_(B) of the target eNB along with a time value (block 710).

According to an example embodiment, along with the Un link subframeallocation S_(B) of the target eNB, the mRN may also receive a timevalue T_(V) that indicates a duration of the validity of the Un linksubframe allocation. The time value T_(V) may be referred to as avalidity duration. The target eNB may basically be ensuring the mRN thatfor the duration of T_(V), the target eNB will not change its Un linksubframe allocation S_(B), i.e., the Un link subframe allocation S_(B)will remain valid for the duration of T_(V). However, once the durationT_(V) expires, the target eNB may no longer be able to ensure that itwill not change its Un link subframe allocation S_(B).

The mRN may participate in a handoff between the source eNB and thetarget eNB (block 715). Once the handoff completes, the mRN may performa check to determine if the duration T_(V) has elapsed since it receivedthe Un link subframe allocation from the target eNB (block 720). As anexample, the mRN may check to determine if the duration T_(V) haselapsed by comparing the current time T with when the duration T_(V)expires, e.g., T>T₀+T_(V), where T₀ represents a time when the mRNreceived the Un link subframe allocation of the target eNB.

If the duration T_(V) has not expired, the mRN may receive Un data usingthe Un link subframe allocation S_(B) of the target eNB (block 725).However, if the duration T_(V) has expired, then the mRN may not beensured that the Un link subframe allocation of the target eNB has notchanged and therefore, the mRN may need to obtain the Un link subframeallocation (new S_(B)) from the target eNB (block 730). Once the mRN hasobtained the Un link subframe allocation (new S_(B)) from the targeteNB, the mRN may receive Un data using the Un link subframe allocation(new S_(B)) from the target eNB (block 735).

FIG. 8 a illustrates a flow diagram of eNB operations 800 in providingUn link subframe allocation to an mRN. eNB operations 800 may beindicative of operations occurring in a source eNB, such as eNB A 205,as the source eNB is serving an mRN that may be moving out of a coveragearea of the source eNB.

As the mRN moves about the coverage area of the source eNB, the mRN mayreach the periphery of the coverage area. As a result, operatingconditions of the mRN may indicate to the source eNB that a handoff witha target eNB is needed. The source eNB may perform a check to determineif the mRN needs to handoff (block 805).

If the mRN needs to handoff to the target eNB, the identity of which thesource eNB may be able to determine based on a location of the mRN and adirection in which it is moving, then the source eNB may request thetarget eNB's Un link subframe allocation S_(B) and a duration T_(V) forwhich the Un link subframe allocation will remain valid (block 810).

According to an example embodiment, in order to reduce Un link subframeallocation sharing overhead, the sharing of the Un link subframeallocation may be one way, from the target eNB of the handoff to thesource eNB of the handoff. To further reduce the Un link subframeallocation sharing overhead, the source eNB may not request the Un linksubframe allocation from the target eNB until a handoff is eminent or isalready in process.

The source eNB may receive the Un link subframe allocation S_(B) and theduration T_(V) from the target eNB (block 815) and send the Un linksubframe allocation S_(B) and the duration T_(V) to the mRN (block 820).

FIG. 8 b illustrates a flow diagram of eNB operations 850. eNBoperations 850 may be indicative of operations occurring in a targeteNB, such as eNB B 210, prior to a handoff, during the handoff, andafter the handoff.

Prior to the handoff, the target eNB may receive a request from a sourceeNB to provide the source eNB the target eNB's Un link subframeallocation S_(B) and a duration T_(V) during which the target eNB willnot change its Un link subframe allocation (block 855). The value of theduration T_(V) may be based on factors such as how long has it beensince the last time the target eNB changed its Un link subframeallocation, Un link performance, Un link error rate, Un linkutilization, a number of mRNs and RNs supported by the target eNB, andthe like.

The target eNB provides to the source eNB its Un link subframeallocation S_(B) and the duration T_(V) (block 860). Until the durationT_(V) expires, the target eNB does not changes its Un link subframeallocation S_(B) (block 865).

During the handoff, the target eNB and the mRN exchange signaling tocomplete the handoff (block 870). After the handoff is complete, thetarget eNB may perform a check to determine if the duration T_(V) haselapsed since the target eNB sent the source eNB its Un link subframeallocation S_(B) and the duration T_(V) (block 875). If the durationT_(V) has not elapsed, then the target eNB may use its Un link subframeallocation S_(B) to send Un data to the mRN (block 880). While FIG. 8illustrates an example embodiment wherein a timer is used during thehandoff process, other mechanisms are possible, such as using ahandshake process.

However, if the duration T_(V) has elapsed, then the target eNB mayupdate its Un link subframe allocation S_(B) (block 885). It is notedthat the update to the Un link subframe allocation may or may not changethe Un link subframe allocation S_(B). However, regardless if the Unlink subframe allocation S_(B) was changed in the update, the target eNBmay send the Un link subframe allocation to the mRN, changed orunchanged (block 890) and the target eNB may use the Un link subframeallocation to send Un data to the mRN (block 895).

As with the solution utilizing the minimum Un link subframe allocation,the sharing of the target eNB's Un link subframe allocation may presenta problem with additional unused HARQ processes during and after thehandoff. The techniques previously presented for addressing theadditional unused HARQ processes may also apply herein.

FIG. 9 illustrates a diagram of a communications device 900.Communications device 900 may be an implementation of a UE of acommunications system. Communications device 900 may be used toimplement various ones of the embodiments discussed herein. As shown inFIG. 9, a transmitter 905 is configured to send control channels,messages, information, and the like, and a receiver 910 is configured toreceive messages, information, and the like. Transmitter 905 andreceiver 910 may have a wireless interface, a wireline interface, or acombination thereof.

A handoff processing unit 920 is configured to generate messages to besent to an eNB as well as process messages from eNBs involved in ahandoff with communications device 900. A backhaul processing unit 922is configured to determine which Un link subframe allocation to utilizeto receive Un data from an eNB serving communications device 900.Backhaul processing unit 922 is further configured to determine whetheror not to use the Un link subframe allocation or wait to receive a newUn link subframe allocation from the eNB. Backhaul processing unit 922may determine between a full Un link subframe allocation or a minimum Unlink subframe allocation of an eNB to use to receive the Un data. A dataprocessing unit 924 is configured to process the Un data received fromthe eNB. A timer 926 is configured to determine if duration T_(V) haselapsed since receiving the eNB's Un link subframe allocation. A HARQprocessing unit 928 is configured to address HARQ process changes, suchas unused HARQ processes, arising from switching the Un link subframeallocations occurring in a handoff. A memory 930 is configured to storethe Un link subframe allocations (e.g., S_(A), S_(B), S_(φ), and thelike), duration T_(V), and the like.

The elements of communications device 900 may be implemented as specifichardware logic blocks. In an alternative, the elements of communicationsdevice 900 may be implemented as software executing in a processor,controller, application specific integrated circuit, or the like. In yetanother alternative, the elements of communications device 900 may beimplemented as a combination of software and/or hardware.

As an example, transmitter 905 and receiver 910 may be implemented as aspecific hardware block, while handoff processing unit 920, backhaulprocessing unit 922, data processing unit 924, timer 926, and HARQprocessing unit 928 may be software modules executing in a processor915, such as a microprocessor, a digital signal processor, a customcircuit, or a custom compiled logic array of a field programmable logicarray.

FIG. 10 illustrates a diagram of a communications controller 1000.Communications controller 1000 may be an implementation of an eNB, a lowpower node, or the like, of a communications system. Communicationscontroller 1000 may be used to implement various ones of the embodimentsdiscussed herein. As shown in FIG. 10, a transmitter 1005 is configuredto send control channels, messages, information, and the like, and areceiver 1010 is configured to receive messages, information, and thelike. Transmitter 1005 and receiver 1010 may have a wireless interface,a wireline interface, or a combination thereof.

A handoff processing unit 1020 is configured to generate messages to besent to a UE as well as process messages from the UE involved in ahandoff with communications controller 1000. Handoff processing unit1020 is also configured to send a request for a target eNB's Un linksubframe allocation prior to or during a handoff. Handoff processingunit 1020 is also configured to send a response to a received requestfor the Un link subframe allocation of communications controller 1000.Handoff processing unit 1020 is also configured to determine a durationT_(V) value.

A backhaul processing unit 1022 is configured to determine which Un linksubframe allocation to utilize to send Un data to a UE. Backhaulprocessing unit 922 is may determine which Un link subframe allocationto utilize based on the duration T_(V). Backhaul processing unit 1022may determine when and/or how to update the Un link subframe allocation.A timer 1024 is configured to determine if duration T_(V) has elapsedsince responding to an eNB's request for the Un link subframe allocationof communications controller 1000. A HARQ processing unit 1026 isconfigured to address HARQ process changes, such as unused HARQprocesses, arising from switching the Un link subframe allocationsoccurring in a handoff. A memory 1030 is configured to store the Un linksubframe allocations, duration T_(V), and the like.

The elements of communications controller 1000 may be implemented asspecific hardware logic blocks. In an alternative, the elements ofcommunications controller 1000 may be implemented as software executingin a processor, controller, application specific integrated circuit, orthe like. In yet another alternative, the elements of communicationscontroller 1000 may be implemented as a combination of software and/orhardware.

As an example, transmitter 1005 and receiver 1010 may be implemented asa specific hardware block, while handoff processing unit 1020, backhaulprocessing unit 1022, timer 1024, and HARQ processing unit 1026 may besoftware modules executing in a processor 1015, such as amicroprocessor, a digital signal processor, a custom circuit, or acustom compiled logic array of a field programmable logic array.

Although the present invention and its advantages have been described indetail, it should be understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of the invention as defined by the appended claims.

What is claimed is:
 1. A method for operating a relay node during ahandoff from a first controller to a second controller, the methodcomprising: receiving a first instruction from the first controller todiscontinue using a first set of wireless backhaul link resourcesallocated to the relay node by the first controller and to temporarilyuse a second set of wireless backhaul link resources dedicated by thesecond controller; and receiving a second instruction from the secondcontroller to discontinue using the second set of wireless backhaul linkresources and to begin using a third set of wireless backhaul linkresources allocated to the relay node by the second controller.
 2. Themethod of claim 1, wherein receiving the first instruction comprisesreceiving a handoff initialization message from the first controller. 3.The method of claim 1, wherein receiving the second instructioncomprises receiving an allocation of the third set of wireless backhaulresources from the second controller.
 4. The method of claim 1, whereinthe second set of wireless backhaul link resources includes a minimumset of wireless backhaul link resources common to the first set ofwireless backhaul link resources and the third set of wireless backhaullink resources.
 5. The method of claim 4, wherein the first controllerand the second controller are part of a communications system includinga plurality of further controllers, and wherein the minimum set ofwireless backhaul link resources is common to a set of wireless backhaullink resources used by each of the further controllers.
 6. The method ofclaim 1, wherein the second set of wireless backhaul link resourcesincludes wireless backhaul link resources dedicated by both the firstcontroller and the second controller.
 7. A method for operating a targetcontroller during a handoff of a relay node, the method comprising:receiving the handoff of the relay node from a source controller, andinstructing the relay node to temporarily use a first set of wirelessbackhaul link resources dedicated by the target controller uponcompletion of the handoff; and transmitting an allocation of a secondset of wireless backhaul link resources to the relay node.
 8. The methodof claim 7, wherein the first set of wireless backhaul link resources isalso dedicated by the source controller.
 9. The method of claim 7,wherein the first set of wireless backhaul link resources is a subset ofthe second set of wireless backhaul link resources.
 10. A relay nodecomprising: a receiver configured to receive a first instruction from afirst controller to discontinue using a first set of wireless backhaullink resources allocated to the relay node by the first controller andto temporarily use a second set of wireless backhaul link resourcesdedicated by a second controller, and to receive a second instructionfrom the second controller to discontinue the use of the second set ofwireless backhaul link resources and to begin the use of a third set ofwireless backhaul link resources allocated to the relay node by thesecond controller; and a processor operatively coupled to the receiver,the processor configured to temporarily use the second set of wirelessbackhaul link resources dedicated by the second controller, and to usethe third set of wireless backhaul link resources allocated to the relaynode by the second controller.
 11. The relay node of claim 10, whereinthe receiver is configured to receive a handoff initialization messagefrom the first controller.
 12. The relay node of claim 10, wherein thereceiver is configured to receive an allocation of the third set ofwireless backhaul resources from the second controller.
 13. The relaynode of claim 10, wherein the second set of wireless backhaul linkresources includes a set of wireless backhaul link resources common tothe first set of wireless backhaul link resources and the third set ofwireless backhaul link resources.
 14. The relay node of claim 10,wherein the second set of wireless backhaul link resources includeswireless backhaul link resources dedicated by both the first controllerand the second controller.
 15. A communications controller comprising: aprocessor configured to receive a handoff of a relay node from a sourcecontroller, and to instruct the relay node to temporarily use a firstset of wireless backhaul link resources dedicated by the communicationscontroller upon completion of the handoff; and a transmitter operativelycoupled to the processor, the transmitter configured to transmit anallocation of a second set of wireless backhaul link resources to therelay node.
 16. The communications controller of claim 15, wherein thefirst set of wireless backhaul link resources is a subset of the secondset of wireless backhaul link resources.
 17. The communicationscontroller of claim 15, wherein the communications controller operatesin a Third Generation Partnership Project Long Term Evolution compliantcommunications system.
 18. A method for operating a relay node during ahandoff from a source controller to a target controller, the methodcomprising: receiving, from a source controller, backhaul linkinformation including an allocation of a target set of wireless backhaullink resources of the target controller dedicated for use of the relaynode upon completion of the handoff; and receiving backhaul link datafrom the target controller over the target set of wireless backhaul linkresources.
 19. The method of claim 18, wherein backhaul link informationfurther includes a validity duration for the target set of wirelessbackhaul link resources, and wherein the target set of wireless backhaullink resources remains unchanged until expiration of the validityduration.
 20. The method of claim 19, wherein receiving the backhaullink data comprises receiving the backhaul link data over the target setof wireless backhaul link resources if the handoff completes prior toexpiration of the validity duration.
 21. The method of claim 19, furthercomprising: receiving an allocation of an updated set of wirelessbackhaul link resources from the target controller, and receiving secondbackhaul link data from the target controller over the updated set ofwireless backhaul link resources if the handing off did not completeprior to expiration of the validity duration.
 22. The method of claim18, wherein the backhaul link information is received prior to thehandoff.
 23. The method of claim 18, wherein the backhaul linkinformation is received during the handoff.
 24. The method of claim 18,wherein the backhaul link information includes a bitmap indicating theallocation of the target set of wireless backhaul link resources.
 25. Amethod for operating a target controller during a handoff of a relaynode, the method comprising: transmitting, to a source controller,backhaul link information including an allocation of a target set ofwireless backhaul link resources dedicated for use by the relay nodeupon completion of the handoff; and transmitting, to the relay node,backhaul link data over the target set of wireless backhaul linkresources.
 26. The method of claim 25, wherein backhaul link informationfurther includes a validity duration for the target set of wirelessbackhaul link resources, wherein the target set of wireless backhaullink resources remains unchanged until expiration of the validityduration, and wherein the transmitting the backhaul link data comprisestransmitting the backhaul link data over the target set of wirelessbackhaul link resources if the handing off completes prior to expirationof the validity duration.
 27. The method of claim 26, further comprisingtransmitting, to the relay node, an allocation of an updated set ofwireless backhaul link resources, and transmitting, to the relay node,second backhaul link data over the updated set of wireless backhaul linkresources if the handing off did not complete prior to expiration of thevalidity duration.
 28. The method of claim 25, further comprisingreceiving a request for the backhaul link information from the sourcecontroller prior to the handoff.
 29. The method of claim 25, furthercomprising receiving a request for the backhaul link information fromthe source controller during the handoff.
 30. A relay node comprising: areceiver configured to receive, from a source controller, backhaul linkinformation including an allocation of a target set of wireless backhaullink resources of a target controller dedicated for use of the relaynode upon completion of a handoff, and to receive backhaul link datafrom the target controller over the target set of wireless backhaul linkresources; and a processor operatively coupled to the receiver, theprocessor configured to process the backhaul link data.
 31. The relaynode of claim 30, wherein the backhaul link information further includesa validity duration for the target set of wireless backhaul linkresources, wherein the target set of wireless backhaul link resourcesremains unchanged until expiration of the validity duration, and whereinthe receiver is configured receive the backhaul link data over thetarget set of wireless backhaul link resources if the hand off completesprior to expiration of the validity duration.
 32. The relay node ofclaim 31, wherein the receiver is configured to receive an allocation ofan updated set of wireless backhaul link resources from the targetcontroller, and to receive second backhaul link data from the targetcontroller over the updated set of wireless backhaul link resources ifthe hand off did not complete prior to expiration of the validityduration.
 33. A communications controller comprising: a transmitterconfigured to transmit, to a source controller, backhaul linkinformation including an allocation of a target set of wireless backhaullink resources dedicated for use by a relay node upon completion of ahandoff, and to transmit, to the relay node, backhaul link data over thetarget set of wireless backhaul link resources; and a processoroperatively coupled to the transmitter, the processor configured togenerate the backhaul link data.
 34. The communications controller ofclaim 33, wherein backhaul link information further includes a validityduration for the allocation of the target set of wireless backhaul linkresources, wherein the target set of wireless backhaul link resourcesremains unchanged until expiration of the validity duration, and whereinthe transmitter is configured to transmit the backhaul link data overthe target set of wireless backhaul link resources if the handoffcompletes prior to expiration of the validity duration.
 35. Thecommunications controller of claim 34, wherein the transmitter isconfigured to transmit an allocation of an updated set of wirelessbackhaul link resources to the relay node, and to transmit secondbackhaul link data to the relay node over the updated set of wirelessbackhaul link resources, if the handoff did not complete prior toexpiration of the validity duration.
 36. The communications controllerof claim 33, further comprising a receiver operatively coupled to theprocessor, the receiver configured to receive a request for the backhaullink information from the source controller.